Triethylene diamine (TEDA), also known as 1, 4-diazabicyclo(2.2.2) octane, is well known on the commercial market, particularly for use as a catalyst or co-catalyst in the production of polyurethane plastics, elastomers and foams. A number of methods are known to the art for preparing and isolating this compound as a product of commercially acceptable purity.
The earliest production of TEDA on a commercial scale was by the methods disclosed in U.S. Pat. No. 2,937,176, employing as starting material an alkylene polyamine. Other patented processes employ as starting material for production of TEDA, mono- or bis-hydroxyethyl piperazine (U.S. Pat. No. 3,166,558); N-aminoethyl piperazine (U.S. Pat. No. 2,985,658); or alkanolamines alone (U.S. Pat. No. 2,977,364) or in admixture with ethylene diamine (U.S. Pat. No. 2,977,363).
By any of the above methods the TEDA is isolated from the reaction mixture as a white crystalline hygroscopic product, containing a small amount of by-product amine compounds. The TEDA product is generally placed on the market for commercial users in fiber drums of about 12 gallon (about 45 liter or 25 kg.) capacity.
With improved techniques of purification of the synthesized TEDA product, by recrystallization or more precise fractionation, the product is recovered having less than about 500 ppm of accompanying by product organic amine impurities. It was found, however, that the purified commercial product of this desired low content of organic amine impurities, when stored in commercial size drum container for even short periods, particularly in a moderately warm environment, tended to form a crust or agglomerate at the top surface of the closed drum, which crust or agglomeration on further standing, penetrated further and further into the contents of the drum, rendering it difficult to scoop the product out of the drum. Without being bound to any particular explanation for the cause of this hardening of the upper layer of the TEDA in the drum, it is believed that there occurs a sublimination of the TEDA followed by its recrystallization forming a bridge between adjacent particles. This condition renders it difficult to remove product from the drum, herein referred to as poor "scoopability".
In initial attempts to avoid such hardening of the TEDA and to improve the facility of its removal ("scoopability") from the shipping containers the addition of talcs and various other additives were tried of the kinds typically employed to improve flow or prevent lumping of crystalline or powdered solid products. These substances were not found successful in improving scoopability of the TEDA product which had been exposed to temperatures above ambient. It was found, for example, that fumed or colloidal silica additives, such as Cab-O-Sil.RTM., when admixed and dispersed through the TEDA product at levels of 200 to 2000 ppm did obtain some improvement in the scoopability if the product remained at ambient temperature or lower. Higher levels of the Cab-O-Sil within the stated range kept the TEDA scoopable for longer time periods. At somewhat warmer temperatures, as in excess of about 35.degree. C., the product hardened in about three days, apparently with little dependence on the level of the additive therein.